Slide rule cursor



June 21, 1949. J. J.- SMIDL SLIDE RULE cunsoa Original Filed Nov. 20, 1944 'INVENTOR. Jase 0h J. Smid/ Reissued June 21, 1949 UNITED S TATES PATENT "fliF 'Fl C-E 23,127 sums RULE CURSOR JosephJ. Smidl, Portland, Oreg. Original No. 2,418,910, dated April 15, 1947, Serial No. 564,196, November 20, 1944. Applica'tionf'or reissue December 30, 1948, S'erial No."70,421

5 Claims. (01. 235-4343) 1 This invention relates generally to scientific instruments and particularly to an attachment for slide rules.

The'mai'n object of this invention is to provide a means'for facilitating slide rule computation and to reduce the chance for error in making such computation.

The secondobject is to free the mind of the slide ruleoperator of the necessity of carrying any figures in his mindin order to place the decimal point correctly when the answer to a problem has been found on the slide rule.

The thirdobject is to free the mind of the operator from the unnecessary retention of values in order to enable him to concentrate on the actual problem at hand and its solution, thereby permitting faster and surer slide rule computations.

Thefourth object is to provide-a means for indicating the decimalpoint place without referring -to any'notes or remembering anything or without making any mental calculations.

Iaccomplish these and other objects in the manner set forthin the following specification as illustrated in the accompanying drawing, in

which Fig. 1 is a front elevation of the device showing same mounted on a portion of a slide'rul'e;

Fig. 2 is a plan of'Fig. 1;

Fig. -3 is a transverse section taken along the lin'e3-3'in Fig. 1;

Fig. 4 1s a front view with the lever guards removed;

Fig. '5 is'a'fr'ont elevation of the annulus and *pawl'mechan'i'sm,with the parts in-front of the same removed for clearness.

Similar numerals refer to similar parts throughout the views.

Referring in detail'to the drawing, there is shown a frame including a runner I whose inturn'ededges I I engage the grooves I2 in the slide 'rule I3. A spring I4 aifords the desired amount of friction between the runner in and the slide rule l3. The transparency I5 is mounted in the "sight opening'of the runner I0 and has on it 'anin'dicator line I6. 'scribedIis now in common use.

The device thus far de- Referring particularly to my invention, same will be seen to consist of a hollow ring H, which .-is secure'clito the front of the-runner I0, and

its inner diameter approximates that of the sight opening of the runnerlil. The ring I1 is provided with a rim I8 around the major portion wot-"its circumference. Within the rim I'll is dispose d a'revolvable annulus I9, which is, provided with evenly spacedlugs '20 on its outer circumference. The interior-edgeZI of .the ring I! is provided with arim 22, on which the annulus I9 is capable of rotation. Anopening 23 is formed in the cover plate 24, formingpart of-ring I7, and

through this openingcan-be seen'one figure 25,

on annulus I9, at one time. 'Ihesefigures may run from zero to plus or'min'us twelve, -in opposite d1rections, and the'figuresare spaced corresponding to the spacing of the lugs so that they will appear inopening 23 sequentially at each operation of lever arms 26R and 26L, asxwill appear.

Portions of the r-im Ifl'are cut away on each side of the opening '23 near the lever arms 26R and "ESL, whose pivots 21 are mounted on the Cover m e 24. SpringsBIlA urge" the outermost;

ends of the levers 2IiR and 26L toward'the opening 23.

Each lever arm 26R and 26L is provided with a-pawl '29, which is urged by a spring '30 through the adjacent cut-away portionof rim I8 into engagement with the .lugs '2'0 when the lever arm 2GB or 26L is moved downwardly. This down- "ward -movement is accomplished by the manual operation thereof by means of thefoperators of free movement of the lever arms referred to.

'Iheguards32 aresecured to the coverplate fl in any convenient manner. It is important that the cut away portions of the rim I8 and the travel of the pawl 29 are-such that only one characteristic at a time can be made to pass the opening 23 so that careless orfast or slow operation of the lever arms-R ar 26L will always produce but one change in the characteristic value. Preferably, the lugs, areomitted from a portion of annulus I9 opposite thezero-figure 25 so that'the device cannot be made to'overrunfrom positive to minus figures'or vice' versa.

In order that the purpose of-the invention may be understoodrit'will-sufficeto state-that each depression of lever lIiRa indves the arimuus I 9 in the direction to bring one of the numerals 25, which has an algebraic value higher than the previously appearing numeral, the amount of increase being the numeral one, into view in the window 23; and each depression of the lever 23L moves the annulus in the opposite direction so that a numeral 25 having a value of one less than the previously appearing numeral will appear in window 23. The operator depresses the proper lever the correct number of times algebraically to add together the characteristics of the numerals being involved in the computation in accordance with known rules for summation of characteristics in slide-rule operations. In utilising the present invention the operator determines the characteristic of each numeral involved in a computation being performed on the slide rule in accordance with the rules of the system he is using and algebraically adds the characteristics together by depressing the proper operating lever or levers the correct number of times. The device therefore serves as a visual reminder of the characteristic of the result of any operation performed on the slide rule.

It can be seen from the foregoing that if the operator wished a plus 4 characteristic, he would simply operate the plunger 26R until he brought the value plus 4 into the opening 23. He would then proceed with his computation and at the time of pointing on" his result, he would merely need to glance at the value in the window or opening 23 in order to determine the location of the decimal point.

I am aware that numerous forms of counters and indicators have been constructed in the past. I therefore do not cover such devices broadly, but I do intend to cover all such forms and modifications thereof as fall fairly within the appended claims.

I claim:

1. A cursor for slide rules comprising a frame adapted to be mounted slidably on a rule, said frame including a hollow ring, an annulus revolvably mounted in said ring, said frame having an opening therein through which a portion of said annulus may be observed, said annulus having lugs formed thereon, a pair of lever arms hinged to said frame, each of said lever arms having a pawl mounted thereon, one of said pawls engaging said lugs to drive same in a clockwise direction and the other pawl engaging said lugs to drive same in a counterclockwise direction, one lug at a time, said annulus being provided with characteristics thereon ranging through sequentially arranged positive values in one direction and negative values in the other direction.

2. A cursor for slide rules comprising a frame, a rotatable annulus mounted within said frame, said annulus having characteristics indicated thereon, said characteristics being sequentially arranged in a series of ascending positive values around one side and a series of ascending negative values around the other side, said annulus having lugs formed thereon, a lever arm mounted at each side of said frame, each of said lever arms having a pawl thereon, said frame being cut away to permit said pawls to engage said lugs and impart movement thereto through one unit of space between characteristics on said annulus, said frame having an opening therein through which one of said characteristics may be viewed.

3. A cursor for slide rules comprising a frame adapted to be slidably mounted on a slide rule, said frame including a hollow ring so arranged as :to permit viewin of the slide rule indicia within 23,127 a f r the confines of the ring, an annulus revolvably mounted in said ring, said annulus having evenly spaced lugs thereon and having numerals thereon spaced according to the spacing of said lugs, said numerals ranging sequentially through a series of plus and minus values in opposite directions around the annulus, said ring having an opening therein through which one of said numerals may be viewed at a time, a pair of manually engageable lever arms hinged to said frame, each of said lever arms having a pawl mounted thereon, spring means urging said pawls to engage said lugs, one of said pawls engaging said lugs to drive said annulus in a clockwise direction and the other of said pawls engaging said lugs to drive said annulus in a counterclockwise direction, other spring means for returning said levers to their starting positions, means on said frame to hold said pawls from engagement with said lugs when said levers are at their starting positions, and means to limit movement of each of said levers to the amount required to withdraw one numeral from said opening and place an adjacent numeral within said opening at each movement thereof.

4. A cursor for slide rules comprising a frame adapted to be slidably mounted on a slide rule, said frame including a hollow ring so arranged as to permit viewing of the slide rule indicia within the confines of the ring, an annulus revolvably mounted in said ring, said annulus having evenly spaced lugs thereon and having numerals thereon spaced accordin to the spacing of said lugs, said numerals ranging sequentially through a series of plus and minus values in opposite directions around the annulus, said ring having an opening therein through which one of said numeral may be viewed at a time, a pair of manually engageable lever arms hinged to said frame, each of said lever arms having a pawl mounted thereon, spring means urging said pawls to engage said lugs, one of said pawls engaging said lugs to drive said annulus in a clockwise direction and the other of said pawls engaging said lugs to drive said annulus in a counterclockwise direction, other spring means for returning said levers to their starting positions, means on said frame to hold said pawls from engagement with said lugs when said levers are at their starting positions, means to limit movement of each of said levers to the amount required to withdraw one numeral from said opening and place an adjacent numeral within said opening at each movement thereof, and means to limit rotation of said annulus in either direction of movement so that the portion thereof opposite the portion having the zero numeral thereon may not rotate past said opening.

5. A cursor for slide rules comprising a frame adapted to be slidably mounted on a slide rule, said frame including a hollow ring so arranged as to permit viewing of the slide rule indicia within the confines of the ring, an annulus revolvably mounted in said ring, said annulus having evenly spaced lugs thereon and having numerals thereon spaced according to the spacing of said lugs, said numerals rangin sequentially through a series of plus and minus values in opposite directions around the annulus, said ring having an opening therein through which one of said numerals may be viewed at a time, a pair of manually engageable lever arms hinged to said frame, each of said lever arms having a pawl mounted thereon, spring means urging said pawls -to engage said lugs, one of said pawls engaging said lugs to drive said annulus in a clockwise direction and the other of said pawls'engaging one numeral from said opening and place an adjaoent numeral within said opening at each movement thereof, and means frictionally resisting rotation of said annulus.

JOSEPH J SMIDL.

No references cited. 

